Method and means for reducing the propelling resistance of vessels

ABSTRACT

A method and apparatus for reducing the resistance or drag of a vessel by affecting the flow condition of the water flowing toward the stem. A flow or stream of water is positively driven forward from the stem of the vessel by a flow device in such a direction and in such a condition of motion that it imparts to the water flowing along the vessel, by superposition, a resulting flow and wave condition of such a character that the resistance to the propelling of the vessel is reduced.

United States Patent lnventor Torbjorn ll. Lundell Grimstagatan 75, Vallinby, Sweden Appl. No. 799,858 Filed Feb. 17, 1969 Patented Dec. 28, 1971 Priority Feb. 19, 1968 Sweden 2163/1968 METHOD AND MEANS FOR REDUCING THE PROPELLING RESISTANCE OF VESSELS 10 Claims, 11 Drawing Figs.

11.8. CI 114/57, 1 14/ 1 51 Int. Cl B63h l/06, B63h 25/46 Field of Search 114/56, 67; l 15/ l l [56] References Cited UNlTED STATES PATENTS 2,330,674 9/1943 Briggs ..L 114/151 3,237,585 3/1966 Winter 114/151 3,442,242 5/1969 Laskeyetal 114/148 420,670 2/1890 Anderl.. 114/67 1,818,705 8/1931 Gay 115/11 Primary Examiner-Andrew H. Farrell At1orneyWoodhams, Blanchard & Flynn ABSTRACT: A method and apparatus for reducing the resistance or drag of a vessel by affecting the flow condition of the water flowing toward the stem, A flow or stream of water is positively driven forward from the stern of the vessel by a flow device in such a direction and in such a condition of motion that it imparts to the water flowing along the vessel, by superposition, a resulting flow and wave condition of such a character that the resistance to the propelling of the vessel is reduced.

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METHOD AND MEANS FOR REDUCING THE PROPELLING RESISTANCE OF VESSELS The present invention relates to a method and a means for reducing the propelling resistance and thus the necessary driving power of ships and vessels, more particularly to devices of the kind mounted in the forebody of the ship in order to produce a drag-reducing effect.

The resistance to which a vessel is exposed in heading through the water relates substantially to two components, friction resistance and wave-forming resistance. It has been known for a long time that said last-mentioned resistance can be affected in a reducing sense by mounting on the lower part of the stem a so-called bulb, i.e., a projecting, rounded, centrally located portion which is able to reduce at certain speeds the resistance of the ship. The common explanation is that the reduction is attributed to the ability of the bulb to create somewhat ahead of the vessel a wave system interfering with the wave caused by the forepart of the vessel itself (the bow wave). At certain suitable speeds this interference brings with it a reduced resistance, but at other speeds an increased resistance. However, the phenomenon not completely known in all details and for all hull configurations, and, as a plausible explanation, it is assumed that the effect of the bulb is conditioned by the fact that it raises ahead of the vessel a wave earlier than the ship stern proper and thus creates the prerequisites for the following drag-reducing phenomenon of resonance or interference. Disregarding the exact explanation of how the complicated flow pattern created by the bulb really arises, it is a fact that the resulting wave system around the vessel becomes flatter or more level, which means a reduced power requirement. It has also been observed that the flow about the afterbody can be affected by a forebody bulb.

A bulb can be provided with various cross-sectional configurations and be fitted into the hull with more or less even transitional sections. Likewise the relative fore and aft position of the bulb on the ship may be varied in order to attain the best effect. On the other hand, as indicated above, in its usual form a bulb can only be constructed in such a way that maximum reduction of power is attained at specified combinations of speed and draft which means, of course, a limitation of its applicability. Further, from a practical point of view a bulb forms an expensive and vulnerable construction which, for example, cannot be used on ships which are intended to proceed in ice.

The invention has for its object to reduce the power requirement in propelling a vessel by affecting in a new way the flow and wave formation ahead of and along the hull of the vessel. This object is attained and the above-indicated inconveniences and limitations connected with the previous bulb constructions are remedied by the device according to the present invention.

Some embodiments of the invention will now be described diagrammatically and by way of example with reference to the annexed drawings, wherein:

FIGS. 1-3 show the forebody of a vessel with and without a bulb and the wave systems related thereto.

FIG. 4 shows an impeller which is intended to drive water forward in accordance with the principles of the invention.

FIG. 5 is a view corresponding to FIG. 4 but shows the impeller provided with a shroud.

FIGS. 6-9 show the impeller built into the ship in various ways.

FIGS. 10 and 11 show how water can be driven or impelled in various ways forwardly from the stem by means of a pump which projects water ahead of the vessel at high velocity through a nozzle.

According to the basic principle of the invention it is postulated that the drag or resistance-reducing effect of the known bulb has its ultimate basis in its ability to raise, as explained above, a wave ahead of the vessel and ahead or the waves of wave system caused by the stem or forebody proper of the vessel. Now, according to the invention there is created instead a wave-developing effect by means of a pumping or impelling unit located in the forebody of the vessel, said unit impelling a stream or jet of water forward in a certain direction to raise ahead of the vessel a wave corresponding to that caused by the bulb.

As may be seen from FIG. I a forebody or bow 10 of a vessel creates a bow wave I2 having substantially the relative position shown in the figure and followed by a wave-trough 12a. If the forebody 10 of FIG. I is provided with a bulb I4, see FIG. 2, this alone would raise, disregarding the influence of the forebody or stem itself, a wave 16 ahead of the vessel, this wave being followed by a wave-trough 16a. Now, by the combined action of the forebody l0 and the bulb 14 the wave pattern shown in FIG. 3 is obtained, that is, a resulting considerably more level wave 18 is created, to which is attributed the reduction of drag.

In applying the invention in its simplest or principally ulterior form the arrangement shown in FIG. 4 is obtained, that is, a forebody 20 of a vessel is provided with a driven impeller 22 supported by suitable bearings on the vessel and rotatably driven by any conventional drive means (not shown) mounted in the vessel. The direction of rotation of the impeller 22 is such that it propels a stream of water forward, as shown by the arrows, this advancing stream of water created a wave 24 ahead of the vessel in analogy with the wave-creating effect of the conventional bulb. According to FIG. 5 the impeller 22 is surrounded by a shroud 26 in order to improve the efficiency of the impeller and concentrate the flow. Also in this case a wave, here designated 28, is raised ahead of the vessel, the direction of the advancing stream of water being variable for optimal effect, such variation of course also being possible in the embodiment according to FIG. 4.

in FIGS. 6 and 7 there is illustrated diagrammatically how the principle of the invention is applied when the necessary pumping unit is built into the forebody. According to FIG. 6 the forebody 30 of a vessel is provided with a centrally located flow tunnel or duct 32 in a vertical plane and having an inlet 31 at the top whose cross-sectional configuration may be rather narrow but high, andan outlet 33 located below said inlet, the duct 32 forming a reversing circuit for the water flowing in at the top, as illustrated by the arrows. In the duct 32 a rotatable pumping wheel or impeller 34 is mounted at a suitable place and imparts to the outflowing water an impulse properly adjusted to the purpose of the invention.-

The arrangement according to FIG. 7 forms substantially the reverse of that shown in FIG. 6; a centrally disposed flow duct 36 positioned in a verticalplane and having its inlet 37 positioned lowermost in the forebody 30' while the outlet 39 is located straight above the opening forwardly. Also in this case rotatable impeller 38 is mounted in a suitable position and driven by a conventional rotatable driven means (not shown).

A further mounting variant is shown in FIGS. 8 and 9, said last-mentioned figure showing a section along the line lX-IX of FIG. 8. In a forebody 40 a flow duct 42 is provided and whose inlet 41 is divided into two branches, one on either side of the bow or stem, as shown in FIG. 9, and terminating in a central discharge opening 43 in the stem, the whole duct 42 extending substantially in a horizontal plane. An impeller 44 is mounted close to the discharge end of the duct.

In all embodiments according to FIGS. 6-9 a portion of the ram pressure of the water approaching the vessel is utilized in the reversing ducts, bringing with it a reduced power requirement on the pump unit.

In the embodiments of the invention described so far it has been a question of putting considerably large masses of water into motion at a comparatively slow speed. The kinetic energy represented by this flowing mass of water may also be utilized within the scope of the invention in the form of a smaller but rapidly flowing mass of water. This would mean, for instance, that a pump unit located in the forebody impels, by a great force and at a high velocity, a comparatively narrow, suitably directed jet of water right forward from the stem. This arrangement is illustrated diagrammatically in FIG. 10. In the stem 50 of a vessel a high-pressure pump unit 52 is built in,

having an inlet or water intake duct 54 suitably located in the forebody. From the pump unit water is fed at a high velocity out through an outlet duct 60 to a nozzle 56 mounted in the stem proper, the nozzle being adjustably mounted on the bow, as by a swivel or ball arrangement, so as to be tumable or swingable. Thus a strong jet can be directed from this nozzle forwardly from the vessel with an effect analogous to that of previous embodiments. As indicated by broken lines the water jet can be directed in various directions by means of the rotatable nozzle 56. FIG. 11 shows the same assembly but is provided with an elongated swingable nozzle tube 58. By means of this tube the area of action of the water jet may thus be moved forward in such cases when such an advancement is calledfor.

As stated above, the preceding diagrammatically shown and disclosed embodiments of the invention merely represent examples of the carrying into effect of the invention, and within the scope of the basic concept a plurality of further variations and modifications are possible.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a vessel having device for reducing the vessels drag or resistance by means of superposition of waves adjacent the bow of the vessel, comprising flow means projecting from the bow of the vessel for forcing or discharging a stream of water forwardly from the bow the vessel to create a wave ahead of the bow of the vessel, said flow means causing the stream of water to be discharged under the waterline of the vessel substantially in the heading direction of the vessel, and drive means associated with said flow means for driving same.

2. A vessel according to claim 1, wherein the flow means includes an impeller centrally disposed below the waterline of the vessel, bearing means rotatably supporting the impeller on the bow of the vessel, and said drive means including an inboard prime mover mounted on the vessel and drivingly connected to the impeller for rotating same.

3. A vessel according to claim 1, wherein inlet means pro vides communication between said flow means and the body of water surrounding the vessel for permitting water to be withdrawn from the surrounding body of water and supplied to said flow means, said flow means causing the withdrawn water to be discharged back into the surrounding body of water at a location disposed forwardly of the bow of the vessel.

4. A vessel according to claim I, wherein said flow means includes a high-pressure pumping plant having at least one intake in the side or bottom of the vessel, and at least one nozzle mounted on the bow of the vessel below the waterline and connected to said pumping plant for discharging a water jet' forwardly of the vessel at high velocity substantially in the heading direction of the vessel.

5. A vessel according to claim 4, wherein the nozzle is mounted recessed into the bow and tumable so that the direction of the water jet may be determined for optimal effect.

6. A vessel according to claim 4, wherein the nozzle is arranged in the form of, or at the tip of, a directional tube projecting from the bow.

7. A vessel according to claim 1, wherein a flow duct is provided in the forebody of the vessel below the waterline, the flow duct including an inlet section disposed for receiving water therein flowing past the vessel, the flow duct also including an outlet section for discharging water therefrom in front of the bow of the vessel, and said flow means including pumping means associated with said flow duct for positively forcing a stream of water out of the outlet section of the flow duct below the waterline of the vessel substantially in the heading direction of the vessel.

8. A method of reducing the resistance of a vessel to motion by affecting the flow condition of the water flowing toward the vessels bow, comprising the steps of positively discharging a stream of water forwardly of the vessel from the bow thereof directly into the water surrounding the vessel so that it imparts to the water flowing along the vessel b superposition, a resulting flow and wave condition w 1c reduces the resistance to the propelling of the vessel through the water, the stream of water being discharged under the waterline of the vessel, and directing the discharged stream of water in the forward direction of motion of the vessel so that the discharged stream of water will have a major component of motion substantially in the heading direction of the vessel.

9. A method according to claim 8, further including the steps of withdrawing water from the body of water surrounding the vessel, changing the direction of movement of the withdrawn water, supplying the withdrawn water to a propelling device, and then discharging the withdrawn water into the surrounding body of water in a stream directly forwardly of the vessel substantially in the heading direction thereof.

10. A method according to claim 8, wherein the stream of water is projected forwardly of the vessel from the bow thereof by flow means projecting therefrom. 

1. In a vessel having device for reducing the vessel''s drag or resistance by means of superposition of waves adjacent the bow of the vessel, comprising flow means projecting from the bow of the vessel for forcing or discharging a stream of water forwardly from the bow the vessel to create a wave ahead of the bow of the vessel, said flow means causing the stream of water to be discharged under the waterline of the vessel substantially in the heading direction of the vessel, and drive means associated with said flow means for driving same.
 2. A vessel according to claim 1, wherein the flow means includes an impeller centrally disposed below the waterline of the vessel, bearing means rotatably supporting the impeller on the bow of the vessel, and said drive means including an inboard prime mover mounted on the vessel and drivingly connected to the impeller for rotating same.
 3. A vessel according to claim 1, wherein inlet means provides communication between said flow means and the body of water surrounding the vessel for permitting water to be withdrawn from the surrounding body of water and supplied to said flow means, said flow means causing the withdrawn water to be discharged back into the surrounding body of water at a location disposed forwardly of the bow of the vessel.
 4. A vessel according to claim 1, wherein said flow Means includes a high-pressure pumping plant having at least one intake in the side or bottom of the vessel, and at least one nozzle mounted on the bow of the vessel below the waterline and connected to said pumping plant for discharging a water jet forwardly of the vessel at high velocity substantially in the heading direction of the vessel.
 5. A vessel according to claim 4, wherein the nozzle is mounted recessed into the bow and turnable so that the direction of the water jet may be determined for optimal effect.
 6. A vessel according to claim 4, wherein the nozzle is arranged in the form of, or at the tip of, a directional tube projecting from the bow.
 7. A vessel according to claim 1, wherein a flow duct is provided in the forebody of the vessel below the waterline, the flow duct including an inlet section disposed for receiving water therein flowing past the vessel, the flow duct also including an outlet section for discharging water therefrom in front of the bow of the vessel, and said flow means including pumping means associated with said flow duct for positively forcing a stream of water out of the outlet section of the flow duct below the waterline of the vessel substantially in the heading direction of the vessel.
 8. A method of reducing the resistance of a vessel to motion by affecting the flow condition of the water flowing toward the vessel''s bow, comprising the steps of positively discharging a stream of water forwardly of the vessel from the bow thereof directly into the water surrounding the vessel so that it imparts to the water flowing along the vessel, by superposition, a resulting flow and wave condition which reduces the resistance to the propelling of the vessel through the water, the stream of water being discharged under the waterline of the vessel, and directing the discharged stream of water in the forward direction of motion of the vessel so that the discharged stream of water will have a major component of motion substantially in the heading direction of the vessel.
 9. A method according to claim 8, further including the steps of withdrawing water from the body of water surrounding the vessel, changing the direction of movement of the withdrawn water, supplying the withdrawn water to a propelling device, and then discharging the withdrawn water into the surrounding body of water in a stream directly forwardly of the vessel substantially in the heading direction thereof.
 10. A method according to claim 8, wherein the stream of water is projected forwardly of the vessel from the bow thereof by flow means projecting therefrom. 